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ABSTRACT: Numerical and field results of a reinforced embankment on soft ground constructed up to failure are compared. The first results were obtained by a model based on the finite element method and the second by pneumatic piezometers (pore pressures), horizontal profile tube and settlement cells (settlements), vertical inclinometers (horizontal displacements) and magnetic induction cells and invar yarns (reinforcement strains). Settlements, strains in the reinforcement (geotextile) and global stability are analysed. Several conclusions are presented. INTRODUCTION The paper analyses and compares numerical and field results of a trial embankment on soft soils concerning preliminary geotechnical studies for the A64 high-way construction, in Guiche, France, 1989. Field results were presented and analysed in detail by Quaresma (1992). Numerical results are obtained by a numerical model based on the finite element method (Borges, 1995). The model uses the following theoretical hypotheses:plane strain conditions; coupled formulation of the flow and equilibrium equations considering the constitutive relations (elasto-plastic models) formulated in effective stresses (extension of Biot''s consolidation theory); utilisation of the critical states model [p,q,q] (Lewis and Schrefler, 1987; Borges, 1995; Borges and Cardoso, 1998; Britto and Gunn, 1987) to simulate the constitutive behaviour of the foundation and embankment soils; utilisation of a hardening elasto-plastic model to simulate the ÇinstantaneousÈ constitutive behaviour of the reinforcement; simulation of the viscous behaviour of the geosynthetic (time-dependent constitutive relations) using a rheological model based on a series of Kelvin''s models (Lopes et al, 1994); simulation of the constitutive behaviour of the soil-geosynthetic interfaces using a hardening elasto-plastic model. calculations are performed by a computer program that, in each analysed (cylindrical) failure surface, compares acting and failure tangential forces, obtained from the results of the numerical model and strength characteristics of the materials.
The Optimal Design For Hybrid Mild-Slope Equation
Wang, Chun-Chin (Department of Safety, Health and Environmental Engineering, Hungkuang University) | Wen, Chih-Chung (Department of Safety, Health and Environmental Engineering, Hungkuang University) | Jhang, Shu-Huei (Department of Safety, Health and Environmental Engineering, Hungkuang University) | Yang, Cheng Hung (Department of Safety, Health and Environmental Engineering, Hungkuang University)
ABSTRACT: In this paper, several settings were considered to distinguish the optimal design to the interaction of small-amplitude monochromatic water waves with steep bottom undulation consisting of multiple sinusoids. Doubly-sinusoidal bars consisting of both slowly-varying components and rapidly-varying components are concluded in the water depth. Zhang et al. (1999) numerical results and numerical calculation values of primary and sub-harmonic Bragg reflection of mean value, standard deviation, maximum error value and percentage of maximum error value ratio to reflection value by changing slowly-varying components and rapidly-varying components are distinguished in this paper. In addition, Guazzelli et al.'s (1992) experimental data and numerical calculation values of primary Bragg reflection mean error values and standard derivation by changing slowly-varying components and rapidly-varying components are also compared in the paper. According to the above comparison results, the optimal design for Hybrid Mild-Slope Equation method are proposed in this paper. INTRODUCTION For linear waves, Berkhoff (1972) used the water depth integral method to derive the Mild-Slope Equation (MSE), which describes the effect of water waves transformations such as shoaling, refraction, diffraction, and reflection by suiting proper boundary condition. Chamberlain and Porter (1995) added the higher-order terms in the MES to propose a Modified Mild-Slope Equation (MMSE). Suh et al. (1997) extended the MSE to develop the time-dependent Hyperbolic type MSE (HMSE), which contains the high order terms of bottom slope term and bottom curvature term. Lee et al. (1998) recast the HMSE into the form of a pair of first-order equation. Hsu and Wen (2001) proposed the time-dependent Parabolic Mild-Slope Equation (PMSE) to solve the HMSE. According to Hsu and Wen's (2001) results, the PMSE has the benefit of saving the storage and computing time for a large computational domain when compared with the HMSE.
Abstract The successful design and installation of large diameter SCR relies on close control of the mechanical properties and the dimensional tolerances used in the manufacture of the line pipe product. Statistical assessment of the resultant properties and process control data has shown in the ability to provide pipe dimensions of up to 20 inch OD and 1.22-inch wall for an SCR application in over 7900 FSW. This paper describes the manufacturing process used to produce a large diameter deepwater riser with closely controlled mechanical and dimensional properties. A statistical presentation of the resultant line pipe properties is included to demonstrate the effectiveness of the production process control parameters. Introduction The use of steel catenary riser (SCR) systems has gained prominence within the past few years. Predominately small diameter SCRs in the range of 6-inch to 12-inch have been used for infield flow line tie-backs; with diameters of up to 18-inch diameter being installed for export service. With the introduction of deepwater semi-submersible production platforms the installation and operation of large diameter SCRs has bought about increased requirements in the mechanical and dimensional characteristics of the pipes. Meeting the vessel response associated with a semi-submersible hull design, regardless of the draught and mooring system, can be difficult. Supplemental specifications have been and will continue to focus on more stringent criteria, such as controlled strength levels, enhanced stain capacity and improved fit-up and fabrication performance. To withstand the demands of high installation loads, and extreme operating conditions, such as loop currents, and hurricane force winds and waves, seamless and longitudinal submerged-arc welded line pipe are being manufactured using the latest in steel making, rolling and line pipe production technology. Unique to the use of longitudinal submerged-arc welded line pipe is the ability to meet pipe end dimensional requirements to minimize offset conditions in the girth welds (hi-lo conditions), thereby reducing stress concentration factors that are used in determining the life expectancy of the riser system. With seamless pipe the ends can be machined (boring operation), whereas longitudinal double submerged-arc welded pipe must obtain these tolerances as manufactured. Deepwater SCR Requirements There are a number of material and dimensional requirements deemed necessary to insure the safe installation and continued operation of a deepwater riser system. The ones chosen for presentation include:Chemical Composition Mechanical & Toughness Properties Dimensional Characteristics Manufacturing Controls Specifics of each will depend on the installation technique and service conditions. Chemical Composition Control of the chemical composition predominantly focuses on weldability, resistance to environmental stress checking and the ability to secure high strength, ductility and toughness. To assist field and shop fabrication welding, the chemical composition is restricted in the form of a carbon equivalent (CE) or cold cracking parameter (Pcm). Usually values of 0.38% and 0.20% are specified as maximum values. A sulfur content of 40 ppm is also required to insure toughness and resistance to environmental degradation. For weld metals, the hydrogen and oxygen contents are verified to insure the integrity of the as deposited properties. Also limits will be specified for chemical elements used in sulfur reduction and de-oxidation of the steel so as not to impair the welding operation.
Abstract Technology might be innovative and exciting but ultimately it's delivered business value that measures success. Oil and gas companies have made huge investments in information systems, networks, and infrastructure. Some projects have been successful while others have been expensive investments with questionable return. So what's the next big wave? Collaboration? Web services? Employee portals? Enterprise application integration? Do any of these technologies matter? To squeeze value out of their IT investment, energy companies must examine how they will leverage technology in the future. Introduction The next technology wave is unlikely to be a flood of innovative advancements. Collaboration, web services, and enterprise application integration may be significant developments, however they will not garner the attention that new technologies have in the past. Rather a wave of newly found fiscal management for Information Technology (IT) will steal the limelight. Many oil and gas companies have made huge investments in IT over the last decade. However, after years of escalating expenditures, the results have often been less than stellar. IT departments have been marked with the stigma of broken promises, poor customer service, and under delivery. IT is under pressure. For example:Despite record earnings in the first half of 2001, a major integrated oil company recently undertook a multimillion dollar cost reduction program slashing IT costs by an estimated 20%. A multi-year IT outsourcing deal at a major pipeline was curtailed to reduce costs. Amultinational engineering company halted the implementation of a runaway ERP implementation at the border, stranding Canadian operations on a legacy mainframe application. Despite these challenges, IT is at the heart of the evolution of every major company in the energy sector. Delivering Value With Information Technology With the glamour of the dot com era behind us, we are now entering a maturing phase of IT. Gone are the days when IT managers can say to business units: "IT will build it and they will come-trust me." Sophisticated consumers of information now demand to know the magnitude and timing for business benefits from IT projects. Strategic Resource or Cost Centre? Many IT departments in the energy sector are managed as cost centres. This reflects positioning in an industry where production activities take precedence. To become a strategic resource, the role of IT must be clearly articulated towards enabling growth. Figure 1 illustrates the three sides of an approach for IT to deliver strategic value: Growth, Productivity, and Cost Reduction. IT has finite capacity and resources. An IT department focused solely on cost reduction will be incapable of effectively capitalizing on opportunities to enable growth or increase productivity. To proactively position as a strategic resource, IT departments must excel in four key areas:Structure for Success Measurable Results Defined Service Determined Leadership Structuring For Success Effective models to strategically deliver IT services have been elusive. In many organizations, a CIO role has been created to provide standards, overall direction, and high-level budget control. Services are commonly distributed through business unit IT departments.
ABSTRACT The destructive effects of shallow water wave action on the underside of horizontal floors, decks, and platforms is evident from the inspection of hurricane damage. In order to provide some knowledge of the pressure distribution under such conditions, a laboratory study was made. Results are generalized through the use of dimensionless parameters and are presented in graphical form. These graphs show maximum and minimum relative pressure intensity and distribution of relative pressure intensity along the underside of the platform, in the general direction of wave motion, for various conditions of relative wave height, relative clearance, relative width, and relative length. INTRODUCTION Inspection of structural damage due to hurricanes along the Gulf Coast has revealed that horizontal floors, decks, and platforms are susceptible to severe damage by shallow water wave action on the underside. In order to gain some knowledge as to pressure intensities associated with such conditions, a laboratory study was undertaken. Although hurricane conditions could not be simulated, the action of shallow water waves on a small scale structure provides useful information as to the nature of the problem. The study was designed to reveal the separate effects of wave height, clearance above still water surface elevation, width of structure, length of structure, and still water depth on pressure intensity along the underside of. the structure, in the general direction of wave motion. This was done by varying each quantity, except depth, from the value associated with a set of common or reference conditions. The results are generalized insofar as possible through the use of dimensionless parameters, length ratios with stillwater depth as the common quantity. There is reason to believe that the motion of a large, storm wave through relatively shallow water may be more nearly that of a solitary wave than that of a wave in an oscillatory wave train. Proceeding on this premise, the waves generated for this study were sufficiently far apart that they were considered to be independent of one another. This means that, for the purposes of this study, such quantities as wave period and wave length are not considered to be significant. DIMENSIONAL CONSIDERATIONS A rather common structural problem along coasts exposed to hurricanes is that having to do with pressure intensity on the rectangular, horizontal underside of floors, decks, and platforms as a result of shallow water wave action. If the study is limited to cases in which a centerline of the rectangular underside is parallel to the general direction of wave motion, the physical quantities which appear to enter the problem are those necessary to describe the pressure intensity, the location at which pressure intensity is determined, the characteristics of the water, the characteristics of the waves, the spatial relation of structure to water, and the geometry of the structure.